1. Field
The present invention relates generally to the field of power, and. more specifically, to the field of minimizing power consumption of electronic components.
2. Background
Minimizing the draw from an internal power source permits electronic devices such as, for example, personal digital assistants (PDAs), mobile telephony devices, personal laptop computers, etc., to operate for extended time periods untethered to an external power source. One methodology for reducing power consumption is based on the premise that the microprocessor cores within such devices need not operate at peak performance levels at all times. If a lower level of performance is allowed, then the clock frequency of a microprocessor core may be lowered. Correspondingly, the minimum supply voltage to the core for supporting that clock frequency may also be lowered. Hence, dynamic voltage scaling (DVS) is a methodology designed to adjust the voltage supplied to a microprocessor core whenever the computational load upon the core changes.
Some past DVS systems were based on duplication of a critical path of the core. In digital signal processing systems, the term “critical path” refers to the longest path between any two storage elements or any two delay elements. In combinational logic circuits, the critical path is the greatest delay path between inputs and outputs.
In one example of a past DVS system, a free-running ring oscillator configured in a feedback loop is used to model the critical path. The supply voltage is fed to the free-running ring oscillator, which outputs a clock signal that may easily be converted into an operating frequency. The operating frequency may be compared to a desired frequency to generate an error value. The error value may then be used to determine the transfer of charge to a capacitor, which is used to generate a new supply voltage. The new supply voltage may be fed back to the free-running ring oscillator to close the loop. Hence, the supply voltage may be adjusted whenever a new clock frequency is requested. Alternative components, such as linear regulators and buck converters, may be used in conjunction with the free-running ring oscillator to achieve the desired results.
However, the DVS systems described above are not optimal since they depend on the measurements of a critical path model, not the measurements of the actual critical path itself.